For modulators in RF systems using I and Q signals, the I and Q signals may be derived from a local oscillator, the I signal being in-phase with the local oscillator signal and the Q signal being 90 degrees out-of-phase with the local oscillator signal. The object of phase regulation is to maintain, as closely as possible, the 90 degree phase difference between the I and Q signals.
At present, for example in I/Q modulators used in digital radio telephones, either a resistance trimmer or a trimmer capacitor is used for regulating the phasing of I and Q signals, used to-control the modulator. The trimmers complicate tuning i.e. the regulating of the phase difference, and this results in additional manufacturing costs. Control is also difficult, since the trimmers must be adjusted through an opening in the shielding body, or the intermediate body enveloping the modulator used to electrically and mechanically shield it. Also, mechanically controllable components are less reliable than fixed components. Furthermore, mechanical solutions determine the location of the trimmers, in which case it is difficult to achieve an optimal electrical solution.